Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$221.25	3.363%	$228.6906	$228.69	$228.70	$228.70
Purchase #2	$77.44	10.396%	$85.4907	$85.49	$85.50	$85.50
Purchase #3	$72.82	5.634%	$76.9227	$76.92	$76.90	$76.90
Purchase #4	$111.71	10.577%	$123.5256	$123.53	$123.55	$123.50
Purchase #5	$218.51	6.834%	$233.443	$233.44	$233.45	$233.40
Purchase #6	$106.92	12.247%	$120.0145	$120.01	$120.00	$120.00
Purchase #7	$186.48	12.456%	$209.7079	$209.71	$209.70	$209.70
7 purchase totals =	$995.13		$1,077.7950	$1,077.79	$1,077.80	$1,077.70